1. Field of the Invention
This invention relates to a process for the catalytic conversion of hydrocarbons, and particularly to those processes involving the catalyzing of reaction of hydrogen with organic compounds containing nitrogen and/or sulfur so as to yield a denitrogenated and/or desulfurized product. More particularly, the invention is directed to the hydrodenitrogenation and/or hydrodesulfurization of hydrocarbon liquids. The invention is especially directed to the catalytic hydrotreating of shale oil containing low sulfur concentrations.
2. Description of the Prior Art
In the refining of liquid hydrocarbon oils derived from mineral oils and other sources, it is often desirable to subject the oil or fraction thereof to hydrotreating. Hydrotreating is a refining process wherein hydrocarbon oils are reacted with hydrogen. Hydrotreating is often employed to reduce the concentration of olefins and oxygen in hydrocarbons but is most commonly employed to reduce the concentration of nitrogen and/or sulfur. Reducing the concentration of nitrogen and sulfur produces a product hydrocarbon which, when eventually combusted, results in reduced air pollutants in the forms NO.sub.x and SO.sub.x. Reducing the concentration of nitrogen is also desirable to protect other refining processes, such as hydrocracking, which employ catalysts which deactivate in the presence of nitrogen.
In general, the hydrotreating of a nitrogen and/or sulfur-containing hydrocarbon oil is carried out by contacting the oil with hydrogen at elevated temperatures and pressures and in the presence of a suitable catalyst so as to convert the nitrogen to ammonia and the sulfur to hydrogen sulfide.
A typical hydrotreating catalyst comprises particles containing a Group VIII active metal component and a Group VIB active metal component supported on a refractory oxide such as alumina. Phosphorus components are commonly incorporated into the catalyst to improve its activity by increasing its acidity. One catalyst which has been successfully employed on a commercial basis consists essentially of molybdenum, nickel, and phosphorus components, usually in their oxide forms, supported on gamma alumina. The metal oxides are then converted to sulfides, typically by contact at elevated temperatures with a hydrogen-hydrogen sulfide mixture or by contact with hydrogen and a hydrocarbon liquid containing organic sulfur compounds. Because of the problems inherent in the storage and transportation of sulfided catalyst, this final sulfiding step is usually carried out, not by the catalyst manufacturer, but by the catalyst user. Thus, the user normally purchases the catalyst in its oxide form, loads the catalyst into a hydrotreating reactor, and therein converts the catalyst metals to sulfides, either by contacting the catalyst with a specially prepared sulfiding mixture or by simply contacting the catalyst with hydrogen and an organic sulfur-containing feedstock. The resultant composition is a catalyst of high activity for hydrodenitrogenation and/or hydrodesulfurization under conventional hydrotreating conditions.
However, in some cases, hydrocarbon oils may contain such a relatively low concentration of sulfur that the sulfided form of the hydrotreating catalyst is difficult to maintain, especially when the catalyst is employed at relatively severe reaction conditions in order to treat difficult-to-remove nitrogen compounds.
Accordingly, it is a major object of this invention to provide a hydrotreating process, and particularly a hydrodenitrogenation and hydrodesulfurization catalytic process, which results in denitrogenation of a given hydrocarbon oil low in sulfur concentration.
It is another object of this invention to provide a catalytic process with excellent hydrodenitrogenation advantages, especially when utilizing a sulfided catalyst to remove organonitrogen compounds.
It is a further object of this invention to provide a catalytic process for hydrotreating a shale oil, particularly an upgraded shale oil, and more particularly, to provide a catalytic hydrodenitrogenation process of a shale oil.
It is a still further object of this invention to provide a catalytic process for hydrotreating a hydrocarbon oil that utilizes an inexpensive form of sulfur.
These and other objects and advantages of this invention will become apparent to those skilled in the relevant art in view of the following description of the invention.